<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <h1 class="text">00:00:00</h1>
  <script>
    var oText = document.querySelector(".text");
    function fun(){
      var dateNow = new Date();
      var h = dateNow.getHours();
      var m = dateNow.getMinutes();
      var s = dateNow.getSeconds();
      oText.innerHTML = h + ":" + m + ":" + s;
    }
    setInterval(fun,1000)


    // 17620000
  </script>
</body>
</html>